In the field of modern architecture, gypsum is a major material used in the construction industry. It is well-known that gypsum boards comprise a gypsum plate formed using powders of minerals, adhesive and other compositions, and lining papers being wrapped on each major surface of the gypsum plate.
Generally, the starch is used as the adhesive in gypsum board. As is well known in the art, the bonding strength between the gypsum plate and the lining papers is positively related to the starch content. That is, in general, higher starch content gives a higher bonding strength between the gypsum plate and the lining paper. However, there is a limitation for the content of the starch that could positively contribute to the bonding of the gypsum. This means that the bonding strength is not improved by adding more starch above a threshold, where the threshold may depend on the application environment.
Meanwhile, the Cl− present in gypsum material, water and additives negatively impacts the bonding of a gypsum board, leading to poor bonding between the paper and the gypsum plate in the final product. This problem typically occurs when the content of Cl− exceeds 300 ppm. Traditionally, using more starch during production of a gypsum board would mitigate the impact of Cl−. However, as mentioned above, there is a limit to the effectiveness of starch at higher addition levels.
Also, in other gypsum product, such as plaster and joint compound, the Cl− present would lead to efflorescence of the gypsum product.
In this regard, there always is a need in the art to improve the bonding strength between the gypsum plate and lining paper in a gypsum board without using more starch therein and at least mitigate the negative impact of Cl−.